1. Field of Art
The present invention relates to an entry control system and an entry control method using visible-light communications for entry control of a facility.
2. Description of Relevant Art
As an entry control system for a facility, such as a building or condominium, of which the entry is limited to specific persons, there is a conventional system employing a card key in which an ID code is stored.
This entry control system includes a card reader for reading an ID code stored in a key, such as a contact card using a magnetic effect or a non-contact card using an RFID (radio frequency identification), and a door lock to be unlocked when the read ID code is legitimate.
Techniques employing such a system have been disclosed in a patent document 1 (Japanese Patent Application Laid-Open Publication No. 2005-036627), and in a patent document 2 (Japanese Patent Application Laid-Open Publication No. 2001-283171).
The patent document 1 has disclosed techniques of an entry control system covering a plurality of doors to be controlled, permitting, even in occurrence of a failure in part of the system, the range of influence to be minimized by a partial degenerated operation, allowing for a suppressed reduction in level of security.
The patent document 2 has disclosed an RFID tag device for preventing an unauthorized use of a lost or stolen key.
Those techniques can be applied to the entry to a facility, allowing for an enhanced security.
However, in application of the patent document 1 and the patent document 2, it is necessary for the user to have actions to make a card reader read a card, and wait in front of a door after an ID code has been read by the card reader, till an unlock following authentication, as a problem.
As a solution thereto, a patent document 3 (Japanese Patent Application Laid-Open Publication No. H09-137649) has disclosed an entry control system, which has a radio wave dispersed from a data reading device installed at a door end to a data communication device portable by the user, and in which a stored data in the data communication device is transmitted by the radio wave to the data reading device, where it is received and processed for analysis to thereby control a door to be locked or unlocked.
Application of this technique allows a door to be unlocked, without needing actions of a user to have a card read nor waiting in front of the door.
Further, for techniques of the patent document 3 employing wireless communications using an electric wave that can be transmitted even into a place across a wall, there is a risk of interception of or obstruction to the electric wave by a malicious third person, but the user or administrator of entry control system is unable to recognize such an interception or obstruction, as a problem.
Further, for wireless communications using an electric wave, restriction of transmission range is difficult, and there may occur a cross-talk, as another problem.